Many information processing systems are configured to include multi-site storage system arrangements. In such arrangements, a multi-site storage system may be distributed over multiple geographically-dispersed locations. A more particular example of a multi-site storage system is a virtual metro cluster, in which the sites may be within different regions of a metropolitan area or other geographic area and interconnected to communicate with one another via a wide area network (WAN). The different sites may correspond, for example, to different data centers of a business or other enterprise.
Each of the sites of the multi-site storage system may replicate file systems associated with the other sites, so as provide file system recovery capability in the event of failure of one or more of the sites. The remote site file systems that are replicated at the given site are also referred to as mirror file systems. Each primary file system of the multi-site storage system may include both cache and disk storage resources, and data written to a file system may be held in cache for a certain period of time before it is sent to disk. Some arrangements of this type provide so-called active-active data access in both primary and replicated file systems, where “active-active” indicates that both primary and replicated file systems of a given site are mounted as read-write file systems. For example, see U.S. Pat. No. 9,582,559, entitled “Multi-Site Storage System with Replicated File System Synchronization Utilizing Virtual Block Storage Appliances,” which is incorporated by reference herein. Despite the significant advantages associated with these arrangements, a need exists for further improvements. For example, it would be desirable to avoid the need for virtual block storage appliances or implementation of corresponding cache coherence protocols.